Incremental load makes it unncecessary to extract all records from the source database each time you reload your document. Instead you retrieve only new records from the database. After retrieving those records you save them locally and next time you load the locally saved records and get the new records from the source database.
You are right. But even then, the basic principle stays the same. Incremental load provides you with a mechanism to load just the updated rows (whether new or modified) from your data source instead of everything.
Saves you a lot of reload time and effort with tables that are quite large and growing.
